Dental caries (cavities) is an infectious disease ubiguitous in civilized populations. Its treatment costs billions of dollars per year and entails considerable discomfort. Caries--the destruction of enamel, dentin, or cementum--has a multifactorial etiology which includes host susceptibility, diet containing fermentable carbohydrates and cariogenic microorganisms. In recent years, certain oral streptococci, notably Streptococus mutans have been associated with caries in man and in experimental animals such as the monkey, rat and the hamster. S. mutans produces the enzyme, glucosyltransferase, which in the presence of sucrose forms high molecular weight dextran-like glucose polymers called glucans or mutans. Studies have suggested the importance of this glucan in the virulence of this organism since its synthesis facilitates microbial adherence to hard surfaces and also contributes to dental plaque formation. In addition, microbial fermentation of glucose and fructose moieties of sucrose results in production of lactic acid, which is involved in demineralization of the tooth surface, thus initiating the carious lesion.
Treatment of experimental animals with antibiotics has shown very significant decreases in the incidence of cariogenic lesions. However, the indigenous bacteria found in the oral cavity and other portions of the alimentary canal play a major role in preventing certain other bacterial diseases through effects collectively referred to as bacterial antagonism. Thus, when broad-spectrum antibiotics, such as tetracyclines, are given in large doses for many days, growth of most of the bacteria that normally thrive in the oral cavity and intestinal tract is suppressed. As a result, antibiotic-resistant strains of potentially pathogenic organisms, normally held in check by antagonistic action, multiply freely and occasionally give rise to a serious, and often fatal, disease, such as acute staphylococcal enteritis. Therefore, the use of general antibiotics does not appear to be a factor for consideration in any attempt to induce protection against dental caries.